The GDPR and Browser Fingerprinting: How It Changes the Game for the Sneakiest Web Trackers

Browser fingerprinting is on a collision course with privacy regulations. For almost a decade, EFF has been raising awareness about this tracking technique with projects like Panopticlick. Compared to more well-known tracking “cookies,” browser fingerprinting is trickier for users and browser extensions to combat: websites can do it without detection, and it’s very difficult to modify browsers so that they are less vulnerable to it. As cookies have become more visible and easier to block, companies have been increasingly tempted to turn to sneakier fingerprinting techniques.

But companies also have to obey the law. And for residents of the European Union, the General Data Protection Regulation (GDPR), which entered into force on May 25th, is intended to cover exactly this kind of covert data collection. The EU has also begun the process of updating its ePrivacy Directive, best known for its mandate that websites must warn you about any cookies they are using. If you’ve ever seen a message asking you to approve a site’s cookie use, that’s likely based on this earlier Europe-wide law.

This leads to a key question: Will the GDPR require companies to make fingerprinting as visible to users as the original ePrivacy Directive required them to make cookies?

The answer, in short, is yes. Where the purpose of fingerprinting is tracking people, it will constitute “personal data processing” and will be covered by the GDPR.

What is browser fingerprinting and how does it work?

When a site you visit uses browser fingerprinting, it can learn enough information about your browser to uniquely distinguish you from all the other visitors to that site. Browser fingerprinting can be used to track users just as cookies do, but using much more subtle and hard-to-control techniques. In a paper EFF released in 2010, we found that majority of users’ browsers were uniquely identifiable given existing fingerprinting techniques. Those techniques have only gotten more complex and obscure in the intervening years.